Coffee roasting process and apparatus

Abstract

A coffee roaster in the form of a rotating drum having internal baffles forming oppositely-pitched helical paths that drive tumbling coffee beans toward the center of the drum in one direction of rotation of the drum and toward the ends of the drum in the other direction of rotation of the drum, the rotating drum being contained within a vessel and providing with a source of gas in the space between drum, the gas being hot enough to effect roasting of coffee beans.

I claim: 
     
       1. A coffee roasting device comprising a stationary outer vessel;   a single rotatable inner drum having a gas impervious wall positioned within and spaced from said outer vessel to form a hot gas space;   an inlet through said outer vessel to pass hot gas into said hot gas space, and an outlet through said outer vessel to remove gas from said hot gas space;   a closable green coffee bean inlet into said inner drum;   first internal baffles forming a helical path adjacent a first axial length of a rotating wall of said inner drum, said helical path pitched to drive particulate material in said drum in a first axial direction upon rotation of said drum;   second internal baffles forming a helical path adjacent a second axial length of rotating wall of said inner drum, said second baffles pitched to drive particulate material in an axial direction opposite said first axial direction upon rotation of said drum; and   means to reversibly rotate said inner drum whereby green coffee beans tumbled within a driven alternately toward the ends of said inner drum and toward the center of said inner drum and in contact with said rotating wall.   
     
     
       2. The process for roasting green coffee beans comprising a) introducing said green coffee beans into the inner drum of a coffee roasting device having a stationary outer vessel; a single rotatable inner drum having a gas-impervious wall positioned within and space from said outer vessel to form a hot gas space; an inlet to said outer vessel to pass hot gas into said hot gas space, and an outlet to said outer vessel to remove gas from said hot gas space; a closable green coffee bean inlet into said inner drum; first internal baffles forming a helical path adjacent a first axial length of a rotating wall of said inner drum, said helical path pitched to drive particulate material in said drums in a said first axial direction upon rotation of said drum; second internal baffles forming a helical path adjacent a second axial length of rotating wall of said inner drum, said second baffles pitched to drive particulate material in an axial direction opposite said first axial direction upon rotation of said drum; and means to reversibly rotate said inner drum;   b) introducing hot gas into said hot gas space;   c) rotating said inner drum in a direction to drive said beans in a first axial direction away from the center and toward the ends of said inner drum for a time sufficient to increase the number of beans at the ends of said inner drum and to deplete the number of beans in the center of said inner drum;   d) reversing the direction of rotation of said inner drum to drive said beams in a second axial direction away from the ends and toward the center of said inner drum for a time sufficient to increase the number of beans at the center of said inner drum and to deplete the number of beans at the ends of said inner drum;   e) repeatedly reversing the direction of rotation of said inner drum for a time sufficient to roast coffee beans;   f) rotating said inner drum in a direction to drive said roasted coffee beans toward a coffee-bean outlet; and   g) removing said roasted coffee beans from said inner drum.   
     
     
       3. The process of claim 2 wherein said removed roasted beans are quenched.